What is DNA?

Nov. 5, 2013

Warm up:1. What is DNA?2. Why do we need to learnabout it?

Your answers should be on the notes page. You have one minute to finish up!

Yesterday’s Exit Ticket

HOW can scientists study traits? What do they actually look at?

… Many of you said “GENES”

Can anyone tell me what a “GENE” is?!!!!

Remember Genetic Engineering?

• Genetic engineering is a technique used by scientists to change the DNA of living organisms.

Designer Babies?! WHAAAAT?!

The Good=•Eliminating Disease•Helping sick siblings

Designer Babies?!

The Bad:•Eventually may reduce variety by selecting “best” traits?•Playing “God”?

Yesterday’s opinions…

20% said… SURE! Social status wouldn’t be affected much more than it already is, it will actually increase equality, it could increase our nation’s education level, HEALTHY BABIES!

12.5% said… I JUST DON’T KNOW!

AND 67.5% said… NO WAY, JOSE!Who knows the side effects down the road, technology is going too far, religious beliefs say you are made they way you are supposed to be, if you aren’t satisfied with how your baby may turn out, DON’T HAVE KIDS! (after all, they are made from YOUR genes, so what is “un-perfect” ?)

So, what is DNA then?

• DNA is a nucleic acid

• DNA stands for Deoxyribonucleic Acid

• DNA – is the genetic material inside the nucleus of

eukaryotic cells.

Remember biomolecules

IT ACTUALLY WINDS UP REALLY TIGHTLY AND FITS

INTO CHROMOSOMES!!!

IT ACTUALLY WINDS UP REALLY TIGHTLY AND FITS

INTO CHROMOSOMES!!!

It is made of DNA!

Deoxyribonucleic Acid

Segment of DNA

CHROMOSOMESNUCLEUS GENES SEGMENTS OF DNA

Which cell organelle is DNA found in (for eukaryotes)?

Do prokaryotes even have DNA???

THE NUCLEUS!

OF COURSE! But, it is not protected by

a nucleus!

Discovering the Structure of DNA

Structure was discovered in 1953 by James Watson and Francis Crick

They were only able to complete the model after x rays taken of

DNA through a microscope by a woman named

Rosalind Franklin revealed the key to determining the true

shape….she was never officially credited with

the discovery

Watch this!:DNA ANIMATION!

What is the purpose, or function, of DNA?

• Stores the genetic information that instructs the cell on which proteins to make.

• So, DNA makes PROTEINS

(both are biomolecules!)

• Responsible for determining all organism’s traits such as eye color, body structure, and enzyme production.

Proteins are responsible for most of these

traits!

The Components of DNA• DNA is a long molecule made up

of repeating individual units of monomers called nucleotides.

– Nucleotides are made up of three parts that are held together by covalent bonds:

1. Sugar

2. Phosphate Group

3. Nitrogenous Base

Phosphate

Nitrogenous Base

DeoxyriboseSugar

In the diagram, what substance is represented by the letter x?

A. Ribose sugar

B. Deoxyribose sugar

C. Phosphate

D. Adenine

Nitrogenous Bases

• DNA contains four nitrogenous bases:1. Adenine (A)

2. Guanine (G)

3. Cytosine (C)

4. Thymine (T)

In DNA, Which Bases Pair?

• Adenine (A) always pairs with Thymine (T)

• Guanine (G) always pairs with Cytosine (C) Covalent

bonds

Watch this!: COMPOSITION OF DNA

In your notes, write in the base pairs for the following:

These bases are held together by hydrogen bonds

What are Hydrogen Bonds?Hydrogen bonds are weak and

they combine the two DNA strands.

It is important that these

middle bonds are weak! Why do you think???

Structure of DNA

• Phosphate Group & Deoxyribose Sugar – Form the backbone or

sides of the ladder.

• Nitrogenous Bases – Form the “steps” of the

ladder or middle of the molecule.

X makes up the backbone along with which other molecule?

A. Ribose sugar

B. Deoxyribose sugar

C. Base-pairs

D. Adenine

•DNA is a DOUBLE HELIX or a twisted ladder.

Pictures Of The Double Helix

THE INSTRUCTIONS

ARE IN THE SEQUENCE

OF NUCLEOTIDES.

The components that make up the genetic code are common to all organisms!

G C

TA

A

A

A T

T

T

G

G

G

C

C

C

DNA of a horse DNA of a human

What is the difference?The difference is in the order of the bases.

The more alike two organisms are, the more alike their order of bases will be.

Information for everything about an organism is carried in the order of bases in their DNA, like a language.

If we all have the same components

of DNA, why do we look different

from other people and from other organisms like

horses or plants?

DNA base pairs genes proteins traits

This sequence of base pairs

is what determines our traits

BUILDING A DNA MODEL:• You should have the following materials:

• 1 piece of white copy paper (watch how I fold it!)• 8 phosphates• 8 sugars• 2 adenine bases• 2 thymine bases• 2 guanine bases• 2 cytosine bases

• Use what you learned today to create a DNA model!

• Before you glue, have me check!

EXIT TICKET QUICK-WRITE:Using as much of the vocabulary below,

describe the structure and function of DNA.

deoxyribose double helix nucleotide Watson and Crick

cytosine

covalent bonds

genetic information

thymine base pair nitrogen base

phosphate 3’ to 5’ 5’ to 3’ protein synthesis

genetic code

adenine nucleus hydrogen bond

guanine traits

YOU HAVE FIVE MINUTES!